Grate construction



@Qi, 9, 1934. L} SAFFQRD 1,976,195

GRATE CONSTRUCTION Filed Marh 28, 1932 'IIIIIIIIIII INVENTOR.

ATTORNEYS.

Patented Oct. 9, 1934 UNITED STATES PATENT GFFICE GRATE CONSTRUCTIONApplication March 28, 1932, Serial No. 601,547

2 Claims.

My invention relates to grates and has particular reference to animproved type of grate structure admirably suited for use in conjunctionwith railroad locomotive boilers.

An object of the invention is to so arrange the grate bar assembly thatthe velocity of the air coming up through the bars will never besuficient to disturb the fire bed. The induced draft type of furnace isutilized in locomotives and there are times, as when the drive wheelsslip while gathering momentum, when a very high vacuum is produced abovethe fire bed by the rapid exhaust of the engine. This produces a rapidrush of air under atmospheric pressure into the ash pit and up throughthe grate and fire bed. The force of such a rush of air is oftensufficient to blow large holes in the fire bed.

A further object of the invention is to secure more effective airdistribution over the entire surface of the grate and provide moreefdcient air cooling of the grate by eddying the air currents for asufiicient space of time and over a sufficient distance to absorb asubstantial amountvof heat during its passage to the fire bed ortop ofthe grate. In this way the temperature of the air is raised to morenearly that required for combustion purposes and more efficientoperation is secured.

Yet another object of the invention is to provide a grate structurecharacterized by theabove defined advantageous features and at the sametime so construct it that it is light in weight and of sufficientlyrigid construction to eliminate the possibility of warping or saggingwhen subjected to the high temperature and substantial weight of thefire bed.

Various other meritorious features of the in vention will be found inthe particular arrangement of parts illustrated in the accompanyingdrawing wherein like numerals refer to like parts throughout the severalfigures and wherein:

Fig. 1 is a front elevation, partly in section,

Fig. 2 is atop plan view, partly broken away and in section,

Fig. 3 illustrates the improved arrangement of grate bars, and

Fig. 4 is a vertical section through the center portion of Fig. l, and

Fig. 5 illustrates a modified form of bar, in section.

Referring now to the drawing, the numeral 10 indicates the ash pit ofthe fire box. A double row of grate units 14 are positioned as indicatedin Figs. 1 and 2 between the respective outside waterlegs 11 and acentral supporting member 12 extending between the rows. Each of theunits embodies a substantially flat upper surface with the exception ofthe raised portions at each end forming the upper part of the supportingsockets 16 and 18 which are adapted to cooperate with the projectinglugs 20 and 22. The supporting sockets 16 and 18 are positioned at theextremities of the axis of each of the grate assemblies and each of thegrates is adapted to rock about these supports for the purpose ofdumping the ashes.

The improved grate construction comprises a pair of superposed rows ofgrate bars, the upper row being composed of bar formations 24 and thelower row being composed of the bar formations 26. While the gist ofthis invention does not include the particular manner in which the grateconstruction is manufactured, it has been found preferable to cast eachassembly 14 as a unit. Under these circumstances the structure may beregarded either as involving a pair of superposed rows of bars or asembodying two spaced apart layers of substantial thickness havingtransverse slots 28 and 30 located in the layers respectively.

Where an integral casting is provided a plurality of ribs extend inparallel relation along the length of each assembly intermediate theupper and lower bar assemblies or layers for the purpose of providingthe necessary strength and rigidity to the structure. 7 These ribs areclearly indicated in Figs. 2 and 4 at 32 and 3a and constitute aneffective heat transfer medium to assist in more rapidly cooling theunits. A central rib 36 extends downwardly, gradually increasing indepth toward the middle of the assembly as clearly illustrated in Fig.1, for the purpose of further increasing the rigidity of the assembly asa whole and more rapidly dissipating the heat from the grate unit.

The outer extremities of the upper layer are turned over as indicated at38 and join the outer extremities of the lower layer to further assistin rigidifying the integral structure and cooling the same.

Depending from the longitudinal axis of each of the grate units 14 is anarm 40 provided with a projecting pin 42 and each row of theseprojecting pins is coupled with a bar 44 extending the length of the rowtransversely of the grate units whereby all of the grate units in a rowmay be rocked simultaneously from one extremity of the fire box.

Referring now to the improved construction more clearly illustrated inFig. 3 of the drawing, it is to be noted that the bars 24 and 26 are soarranged that the upper bars are staggered in bars 24 is chamfered asindicated at 52 and it' will be noted that if the chamfered portion werecontinued on in its straight line direction downwardly it wouldsubstantially intersect the upperside edges respectively of the lowerbars 26.

The grate structure defined above provides what may be regarded asnarrow cross slots directly over the web section below for the purposeof eddying the air currents as they travel upwardly from the ash pan 54below. The passage of the air being so baffled, it is not only forced totravel over a longer path and therefore absorb a greater amount of heatwhereby more eificient combustion is secured, but its velocity is cutdown so as not to disturb the fire bed on the grate. Furthermore, byvirtue of the peculiar arrangement of the grate bar structures and theirrelationship to one another, the air currents coming up through the ashpan below are split whereby the potential heat which the upwardlydirected air is capable of absorbing is further increased. It will benoted that the lower web section comprising the bars 26 effectivelybaiiles and divides the air, reducing the velocity and flow from belowby directing the air currents toward each other from opposite directionsas they approach the slots 28 between the upper bars 24. It is thissplitting of the air currents and the increase in their length of travelwhich facilitates the efficiency and maintains the uniformity of thefire bed.

The double trussed design equalizes the load and permits a light rigidconstruction which will not warp or sag under the most severe service.

As indicated in Fig. 3 the spacing between the bars of the upper row maybe less than that between the bars of the lower row, although theimportant point is to baiile the upper slot 28 by the lower bar 26. Thevelocity of the air is somewhat decreased as it reaches the top of thegrate by reason of the bafiled passage thus provided.

While the structure has been illustrated as an integral casting, it willbe apparent to those skilled in the art that the assembly could bedesigned in such manner as to utilize a pair of units for the upper andlower assemblies without diminishing the advantages secured except theimportant matter of heat transfer from the upper to the lower bars.

A somewhat modified form of upper bar 25 has been illustrated in Fig. 5.The lower portion of each bar 25 in this upper row includes an arcuaterecessed portion for the purpose of further assisting in creating eddycurrents for cooling purposes. A circular or swirling motion of the airis brought about through this arcuate recess extending along the lengthof the bar on the lower side thereof which permits contact between thebar and the airfor a greater period of time.

While certain preferred modifications have been illustrated herein Iwish to be limited only by the scope of the appended claims.

What I claim is: r I

1. A grate bar unit comprising an upper and lower series of transversespaced parallel bars in overlapping staggered relation to one another,said bars being formed as an integral unit and merging into a continuousvertical flange at each end, each flange being common to all theparallel bars, and a rigidifying and strengthening rib integral withsaid bars extending longitudinally between the same, the bottom face ofeach of the upper series of bars including a recess extending the lengththereof.

2. A grate bar unit comprising an upper and lower series of transversespaced parallel bars in overlapping staggered relation to one another,said bars being formed as an integral unit and merging into a continuousvertical flange at each end, each flange being common to all theparallel bars, and a rigidifying and strengthening rib integral withsaid bars extending'longi- 'tudinally between the same, the bottom faceof each of the upper series of bars including a recess extending thelength thereof, said recess being of a width approximately equal to thespace between each of the lower series, and in substantial verticalalignment therewith.

LAFAYETTE E. SAFFORD.

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